Minimal example for confirming that docker containers can DNS resolve other containers by name as well as external URLs. Based on the Docker networking tutorial here: https://docs.docker.com/engine/network/tutorials/standalone/

troubleshooting_docker_dns.sh

set -x

# Create resources
docker network create --driver bridge alpine-net
docker run -dit --name alpine1 --network alpine-net alpine ash
docker run -dit --name alpine2 --network alpine-net alpine ash
docker network inspect alpine-net

# Test connectivity
docker exec -t alpine1 ping -c 3 alpine2
docker exec -t alpine1 ping -c 3 google.com
docker exec -t alpine1 nslookup alpine2

# Clean up
docker container stop alpine1 alpine2
docker container rm alpine1 alpine2
docker network rm alpine-net